If $x \boxdot y = 2x-7y$ and $x \diamond y = x+4y$, find $(2 \diamond 0) \boxdot -3$.
First, find $2 \diamond 0$ $ 2 \diamond 0 = 2+(4)(0)$ $ \hphantom{2 \diamond 0} = 2$ Now, find $2 \boxdot -3$ $ 2 \boxdot -3 = (2)(2)-(7)(-3)$ $ \hphantom{2 \boxdot -3} = 25$.